Decorative laminate and method for manufacturing same

ABSTRACT

A decorative laminate includes a decorative layer composed of a resin impregnated decorative sheet and a core layer composed of plural resin impregnated core sheets of core paper, wherein an exposed sheet at a bottom of the decorative laminate is subjected to a parchment treatment.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/735,202, entitled “DECORATIVE LAMINATE AND METHOD FORMANUFACTURING SAME,” filed Dec. 10, 2012

FIELD OF THE INVENTION

The invention relates to a resin impregnated decorative laminate andmethod for manufacturing same.

BACKGROUND

Decorative laminates are generally constructed from plural layers ofsynthetic resin impregnated paper sheets bonded under heat and pressureto form a unitary structure. With regard to the manufacture of highpressure laminates, the decorative laminate sheet assembly includes atleast a core of one or more phenol formaldehyde resin impregnated sheetsand a melamine impregnated decorative sheet. The decorative sheet may befurther covered with a transparent melamine impregnated overlay layer.

The decorative sheet provides the laminate with an attractiveappearance. The decorative sheet, and the overlay layer, dictate thesurface characteristics of the decorative laminate. For example, thecomposition of the decorative sheet and overlay layer dictates thedecorative laminate's resistance to chemical agents, heat, light, impactand abrasion.

Decorative sheets are commonly manufactured from high quality 60-205grams/meter², pigment filled, alpha cellulose paper impregnated with awater alcohol or water solution of melamine-formaldehyde resin. Theresin impregnated decorative sheets are subsequently dried, partiallycured, and finally cut into sheets. The pigment filled, alpha cellulosepaper of the decorative sheet, may include a solid color, a decorativedesign, or a roto-gravure reproduction of natural materials, such as,wood, marble, leather, abstract design, etc. The aestheticcharacteristics of the cellulose paper are revealed as the laminate'sdecorative design upon completion of the manufacture of the decorativelaminate.

The core, or base, functions to impart rigidity and impact resistance tothe laminate. Prior to stacking, the paper sheets of the core areimpregnated with a water alcohol or water solution of phenolformaldehyde resin, dried and partially cured in a hot oven. The curedlaminate is then cut into predetermined shapes used to assemble thelaminate layer. The core may, for example, include a plurality of sheetsof 160 to 550 grams/meter² basis weight Kraft paper, impregnated withphenol formaldehyde resin, wherein the phenol formaldehyde resin isgenerally 25% to 35% of the final weight of the impregnated or coatedcore sheet. The Kraft paper is impregnated throughout and bonded with asubstantially cured phenol formaldehyde resin which has been convertedto a thermoset state during the initial laminating step.

A solid substrate may be bonded to the laminate where additionalrigidity is required. Substrates are generally composed of a pre-curedplastic laminate, such as glass fiber-reinforced thermoset polyesterresin laminates and the like; a wood product, such as hardboard, woodwaste or particle boards, plywood and the like; a mineral base board,such as, cement-asbestos board, sheet rock, plaster board, and the like;or a combination of substrates. The substrate is commonly applied to thephenol formaldehyde resin impregnated sheets making, up the core onlyafter the laminate lay-up is pressed and heated to form the finaldecorative laminate.

Decorative laminates are generally manufactured by stacking the resinimpregnated core sheets, the decorative sheet and the overlay layer toform a laminate sheet assembly, or laminate lay-up. The laminate lay-upis placed between steel press plates and subjected to temperatures inthe range of about 121° C.-160° C., preferably 131° C., and pressure ofabout 56.24 kg/cm²-112.48 kg/cm², preferably 85 kg/cm² for a timesufficient to consolidate the laminate and cure the resins (generallyabout 25 minutes to an hour). The pressure and heat force the resin inthe paper sheets to flow, cure and consolidate the sheets into a unitarylaminated mass referred to in the art as a high pressure decorativelaminate. Finally, the formed decorative laminate is bonded to areinforcing substrate, such as, plywood, hardboard, asbestos board,particle board or the like.

Multiple laminate lay-ups are commonly pressed at the same time. Whenthe laminate lay-ups are stacked, care must be taken to ensure that thelaminate sheet assemblies do not stick together after the application ofheat and pressure. Where the bottom sides of the laminate lay-ups arepositioned in a facing relationship during the application of heat andpressure, a release agent is commonly applied to the bottom sheets ofthe laminate lay-ups such that the bottom sheets do not stick togetherand may be readily separated after the application of heat and pressure.Thereafter, the bottom layer of resulting decorative laminate must besanded to remove the release agent before the decorative laminate may beadhesively bonded to a substrate. Consequently, the use of these releaseagents adds expense and processing time to the manufacture of decorativelaminates.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide adecorative laminate including a decorative layer composed of a resinimpregnated decorative sheet and a core layer composed of plural resinimpregnated core sheets of core paper. An exposed sheet at the bottom ofthe decorative laminate is subjected to a parchment treatment.

It is also an object of the present invention to provide a decorativelaminate wherein the plural resin impregnated core sheets areimpregnated with phenol formaldehyde resin.

It is another object of the present invention to provide a decorativelaminate including an overlay paper layer positioned on top of thedecorative layer.

It is a further object of the present invention to provide a decorativelaminate wherein the overlay paper layer is preferably a melamineimpregnated paper layer.

It is also an object of the present invention to provide a decorativelaminate wherein the decorative sheet is 60-205 grams/meter², pigmentfilled, alpha cellulose paper impregnated with a water alcohol or watersolution of melamine-formaldehyde resin.

It is another object of the present invention to provide a decorativelaminate wherein the core layer is composed of an upper first resinimpregnated core sheet of Kraft paper and a bottom second resinimpregnated core sheet of Kraft paper.

It is a further object of the present invention to provide a decorativelaminate wherein the first and second resin impregnated core sheets are160-550 grams/meter² resin impregnated Kraft paper.

It is also an object of the present invention to provide a decorativelaminate wherein the upper first resin impregnated core sheet isimpregnated with a phenol formaldehyde resin composition and ispartially cured.

It is another object of the present invention to provide a decorativelaminate wherein the upper first resin impregnated core sheet isimpregnated with phenol formaldehyde resin such that the phenolformaldehyde resin is 25% to 35% of a final weight of the upper firstresin impregnated core sheet.

It is a further object of the present invention to provide a decorativelaminate wherein the bottom second resin impregnated core sheet issubjected to a parchment treatment.

It is also an object of the present invention to provide a decorativelaminate wherein the bottom second resin impregnated core sheet ispreferably 160 to 550 grams/meter² basis weight Kraft paper.

It is another object of the present invention to provide a decorativelaminate wherein the bottom second resin impregnated core sheet issubjected to the parchment treatment prior to being impregnated withresin.

It is a further object of the present invention to provide a decorativelaminate wherein the bottom second resin impregnated core sheet includesa first side and second side, and the second side is a lower surfacethat is ultimately exposed and bonded to a substrate.

It is also an object of the present invention to provide a decorativelaminate wherein the second side is subjected to a parchment treatment.

It is another object of the present invention to provide a decorativelaminate wherein the parchment treatment is achieved using sulfuricacid.

It is a further object of the present invention to provide a laminatelay-up comprising a decorative layer composed of a resin impregnateddecorative sheet and a core layer composed of plural resin impregnatedcore sheets of core paper. An exposed sheet at the bottom of thedecorative laminate is subjected to a parchment treatment.

Other objects and advantages of the present invention will becomeapparent from the following detailed description when viewed inconjunction with the accompanying drawings, which set forth certainembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the decorative laminate in accordance with oneembodiment of the present disclosure.

FIG. 2 is a detailed schematic of the bottom second resin impregnatedcore sheet of the decorative laminate disclosed in FIG. 1.

FIG. 3 is a schematic of the stacking and manufacturing process employedin accordance with the present invention.

DETAILED DESCRIPTION

Referring now to the drawings, an embodiment of the high pressuredecorative laminate 10 disclosed herein is illustrated in FIG. 1. Itshould be appreciated that the illustrated embodiment is merely anexample. Therefore, the details disclosed herein are not to beinterpreted as limiting, but merely as a basis for teaching one skilledin the art how to make and/or use the decorative laminate of the presentdisclosure.

Briefly, and as will be described in greater detail below, thedecorative laminate 10 includes a decorative layer 12 and a core layer16. The decorative layer 12 is composed of a resin impregnateddecorative sheet 14. The core layer 16 is composed of plural resinimpregnated sheets of core paper 18 a and 18 b (sometimes referred toherein as “resin impregnated core sheet”), which is impregnated withphenol formaldehyde resin. As will be explained below in greater detail,the lowermost resin impregnated core sheet 18 b, that is, the exposedsheet at the bottom of the decorative laminate 10 is subjected to aparchment treatment. The decorative laminate 10 is manufactured by firstpreparing the resin impregnated decorative sheet 14 and the resinimpregnated core sheets 18 a, 18 b. As shown with reference to FIG. 3,the resin impregnated decorative sheet 14 and resin impregnated coresheet 18 are layered to form a laminate lay-up 30 a, 30 b and thelaminate lay-up is heated and pressed to consolidate and cure thelaminate 10.

In accordance with an embodiment of the present disclosure, the highpressure decorative laminate 10 includes an overlay paper layer 20, adecorative layer 12, and a phenol formaldehyde resin core layer 16composed of two resin impregnated core sheets 18 a, 18 b. It should beappreciated, however, that the layering pattern may be varied, somewhat,without departing from the spirit of the present disclosure.

The overlay paper layer 20 is preferably a melamine impregnated paperlayer. The overlay paper layer 20 is preferably manufactured from a lowbasis weight transparent sheet impregnated with resin, for example,melamine. The resin impregnated overlay paper layer 20 is subsequentlydried, partially cured and finally cut into sheets. While the paper mayexhibit opaque properties prior to heating and pressing, the overlaypaper layer 20 in the final fabricated laminate is preferablytransparent to permit viewing of the decorative sheet 14 positioneddirectly beneath the overlay paper layer 20.

The decorative layer 12 is composed of a conventional decorative sheet14 positioned directly beneath the overlay paper layer 20. When thelaminate is fully heated and pressed, as will be discussed in detailbelow, the overlay paper layer 20 becomes translucent, fully exposingthe decorative layer 12. The decorative layer 12 is chosen from a widearray of sheets. For example, the decorative layer 12 may be a solidcolor (for example, white) or may include an aesthetically appealingpattern.

The overlay paper layer 20 and the decorative layer 12 also dictate thesurface characteristics of the final decorative laminate 10. Forexample, the composition of the overlay paper layer 20 and decorativelayer 12 dictate the decorative laminate's resistance to chemicalagents, heat, light, shock and abrasion.

As discussed above, the decorative layer 12 is composed of a sheet ofdecorative paper 14. The decorative sheets are commonly manufacturedfrom high quality 60-205 grams/meter², pigment filled, alpha cellulosepaper impregnated with a water alcohol or water solution ofmelamine-formaldehyde resin. The decorative paper 14, in accordance withan embodiment of the present disclosure, is impregnated with a resincontent of approximately 50% or greater. The resin impregnateddecorative sheets 14 are subsequently dried, partially cured, andfinally cut into sheets. The pigment filled, alpha cellulose paper ofthe decorative sheet may include a solid color, a decorative design, ora roto-gravure reproduction of natural materials, such as, wood, marble,leather, etc. The aesthetic characteristics of the cellulose paper arerevealed as the laminate's decorative design upon completion of thedecorative laminate 10.

The core layer 16 is preferably composed of first and second resinimpregnated sheets of Kraft (or core) paper 18 a, 18 b although othermaterials, and volume of sheets, may be used without departing from thespirit of the present disclosure. For example, the core layer 16includes two sheets of 160-550 grams/meter² resin impregnated Kraftpaper 18 a, 18 b. The Kraft paper of the upper first resin impregnatedcore sheet 18 a is processed in a traditional manner and is, therefore,impregnated with a phenol formaldehyde resin composition and ispartially cured (β-staged). In accordance with a preferred embodiment,the upper first resin impregnated core sheet 18 a is impregnated withphenol formaldehyde resin such that the phenol formaldehyde resin isgenerally 25% to 35% of the final weight of the impregnated or coatedcore sheet.

With regard to the bottom second first resin impregnated core sheet 18b, the Kraft paper is preferably 160 to 550 grams/meter² basis weightKraft paper. However, and before the Kraft paper is impregnated withphenol formaldehyde resin, the Kraft paper of the bottom second resinimpregnated core sheet 18 b is subject to a parchment treatment.

In particular, and with reference to FIG. 2, the Kraft paper from whichthe bottom second resin impregnated core sheet 18 b includes a firstside 22 and second side 24. The first side 22 is the upper surface thatwill be in a facing relationship with the upper first resin impregnatedcore sheet 18 a, and the second side 24 is the lower surface that willultimately be exposed and bonded to a substrate after manufacture of thedecorative laminate 10. As such, the second side 24 is subjected to aparchment treatment using sulfuric acid. In particular, second side 24is subjected to sulfuric acid which hydrolyses and solubilizes thecellulose present in the pulp wood fibers of the Kraft paper. The paperweb is then washed in water, which stops the hydrolysis of the celluloseand causes a kind of cellulose coating to form. The paper may then bedried.

More particularly, and in accordance with a preferred embodiment, atreatment composition of sulfuric acid (H₂SO₄) at a concentration to 64%to 74% is prepared (in solution with water (H₂O). It is appreciated thetreatment composition of sulfuric acid is preferably prepared by addinghighly concentrated H₂SO₄ (for example, a solution of 98% H₂SO₄) towater with stirring until a desired concentration is achieved. Thesecond side 24 of the bottom second resin impregnated core sheet 18 b isbrushed with the sulfuric acid composition. Immediately after thesulfuric acid composition is applied to the second side 24 of the bottomsecond resin impregnated core sheet 18 b the bottom second resinimpregnated core sheet 18 b is subjected to pressure using a pressureroller. Thereafter, the bottom second resin impregnated core sheet 18 bis submerged in a water bath and then again subjected to pressure usinga pressure roller. Finally, the sulfuric acid is neutralized bysubmerging the bottom second resin impregnated core sheet 18 b in a bathof neutralizing agent composed of a 30% concentration of ammoniumhydroxide (NH₄OH) (in solution with water (H₂O) and once again subjectedto pressure using a pressure roller. It is appreciated the neutralizingagent of a 30% concentration of ammonium hydroxide is preferablyprepared by adding highly concentrated ammonium hydroxide to water withstirring until a desired concentration is achieved. Without thisneutralization step any sulfuric acid remaining in the paper causes arapid degradation of the paper; the paper turns black and losesstructural strength. The bottom second resin impregnated core sheet 18 bis then dried and ready for the application of phenol formaldehyde resinto the first side 22 thereof. In accordance with a preferred embodiment,the Kraft paper is dried in an oven. This drying process removes waterand also removes any ammonia retained in the paper. When the dried paperis removed from the oven it does not smell of ammonia. Residual ammoniawould change the curing kinetics of the subsequent impregnation withphenolic resin.

The bottom second resin impregnated core sheet 18 b resulting from theparchment process described above shows excellent water holdoutcharacteristics and release characteristics. In addition, cross sectionswere done to determine the depth of the parchment on the Kraft paperwith results showing a thickness of 0.04 mm-0.06 mm along the secondside 24 being parched by way of the parchment process described above.This accounts for 0.04 mm-0.06 mm out of a total thickness of 0.5 mm forthe Kraft paper making up the bottom second resin impregnated core sheet18 b.

It is appreciated that although the sulfuric acid composition wasapplied using a brushing technique in the process described above, thesteps outlined above may be achieved using line processes (for example,rollers and baths) commonly employed in the laminate industry. It isfurther appreciated, the present treatment process works well withstandard Kraft paper (such as 100% virgin fiber, 100% recycled fiber, ora combination of virgin and recycled fibers; 100% virgin newsprint, 100%recycled newsprint, or a combination of virgin fiber and recycled fiber)used in the high pressure decorative laminate industry (for example,saturated grade Kraft paper as would be used in the preparing of theupper first resin impregnated core sheet 18 a.

After parchment treatment, the first side 22 of the bottom second resinimpregnated core sheet 18 b is impregnated with phenol formaldehyderesin in a traditional manner. As a result of the parchment treatment, abarrier is formed along the second side 24 of the bottom second resinimpregnated core sheet 18 b preventing resin from adjacent laminatelay-ups for intermixing and bonding adjacent laminate together. Becausethe second side 24 retains many of the characteristics of untreatedresin impregnated Kraft paper, the bottom surface, that is, the secondside 24 of the second resin impregnated core sheet 18 b, of the formedlaminate 10 will still adhere to various substrates using the sameadhesives that are traditionally used. However, and contrary to previouspractice, it is not necessary to sand the second side of the bottomsecond resin impregnated core sheet. The advantage to using theparchment treatment for facilitating release between the bottom coresheets of adjacent laminate lay-ups is that it eliminates the sandingprocess needed remove release agents and the resulting laminates willstill adhere using the same adhesives that would be used on sandedlaminate. This eliminates the energy required for sanding, theapplication of the release agents and the time needed for sanding.

Once the appropriate layers of the laminate are formed, the sheets 14,18 a, 18 b, 20 are stacked in a conventional manner (with the bottomsecond resin impregnated core sheet 18 b at the bottom of the laminatelay-up and the second side 24 of the bottom second resin impregnatedcore sheet 18 b facing the outwardly away from the remainder of thelaminate lay-up. As shown in FIG. 3, a first laminate lay-up 30 astacked as described above is then stacked with a second laminate lay-up30 b stacked as described above with the second sides 24 of the bottomsecond resin impregnated core sheets 18 b positioned in a facingrelationship. The first and second laminate lay-ups 30 a, 30 b are thenbetween steel press plates 40 with the overlay sheets 20 of therespective first laminate lay-up 30 a and the second laminate lay-up 30b in direct contact with the steel press plates 40. The laminate stacksare then subjected to temperatures in the range of 121° C.-160° C.,preferably 131° C., and pressure of about 56.24 kg/cm²-112.48 kg/cm²,preferably 85 kg/cm² for a time sufficient to consolidate the laminateand cure the resins (generally about 25 minutes to an hour). Thelaminates are then cooled for approximately 10 minutes under pressurebefore it is ready for further processing in preparation for its use inthe manufacture of various products.

While specific temperatures, pressures and times are described above, itshould be appreciated that a variety of pressing techniques may be usedwithout departing from the spirit of the present disclosure.

The pressure and heat force the resin in the paper sheets to flow, cureand consolidate the sheets into a unitary laminated mass referred to inthe art as a decorative high pressure laminate. Generally, more than onelaminate is formed at one time.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by appendedclaims.

1. A decorative laminate, comprising: a decorative layer composed of aresin impregnated decorative sheet; and a core layer composed of pluralresin impregnated core sheets of core paper; wherein an exposed sheet ata bottom of the decorative laminate is subjected to a parchmenttreatment.
 2. The decorative laminate according to claim 1, wherein theplural resin impregnated core sheets are impregnated with phenolformaldehyde resin.
 3. The decorative laminate according to claim 1,further including an overlay paper layer positioned on top of thedecorative layer.
 4. The decorative laminate according to claim 3,wherein the overlay paper layer is preferably a melamine impregnatedpaper layer.
 5. The decorative laminate according to claim 1, whereinthe decorative sheet is 60-205 grams/meter², pigment filled, alphacellulose paper impregnated with a water alcohol or water solution ofmelamine-formaldehyde resin.
 6. The decorative laminate according toclaim 1, wherein the core layer is composed of an upper first resinimpregnated core sheet of Kraft paper and a bottom second resinimpregnated core sheet of Kraft paper.
 7. The decorative laminateaccording to claim 6, wherein the first and second resin impregnatedcore sheets are 160-550 grams/meter² resin impregnated Kraft paper. 8.The decorative laminate according to claim 6, wherein the upper firstresin impregnated core sheet is impregnated with a phenol formaldehyderesin composition and is partially cured.
 9. The decorative laminateaccording to claim 8, wherein the upper first resin impregnated coresheet is impregnated with phenol formaldehyde resin such that the phenolformaldehyde resin is 25% to 35% of a final weight of the upper firstresin impregnated core sheet.
 10. The decorative laminate according toclaim 6, wherein the bottom second resin impregnated core sheet issubjected to a parchment treatment.
 11. The decorative laminateaccording to claim 10, wherein the bottom second resin impregnated coresheet is 160 to 550 grams/meter² basis weight Kraft paper.
 12. Thedecorative laminate according to claim 10, wherein the bottom secondresin impregnated core sheet is subjected to the parchment treatmentprior to being impregnated with resin.
 13. The decorative laminateaccording to claim 12, wherein the bottom second resin impregnated coresheet includes a first side and second side, and the second side is alower surface that is ultimately exposed and bonded to a substrate. 14.The decorative laminate according to claim 13, wherein the second sideis subjected to a parchment treatment.
 15. The decorative laminateaccording to claim 14, wherein the parchment treatment is achieved usingsulfuric acid.
 16. A laminate lay-up, comprising: a decorative layercomposed of a resin impregnated decorative sheet; and a core layercomposed of plural resin impregnated core sheets of core paper, whereinan exposed sheet at a bottom of the decorative laminate is subjected toa parchment treatment.
 17. The laminate lay-up according to claim 16,wherein core layer is composed of an upper first resin impregnated coresheet of Kraft paper and a bottom second resin impregnated core sheet ofKraft paper.
 18. The laminate lay-up according to claim 17, wherein thebottom second resin impregnated core sheet is subjected to a parchmenttreatment.
 19. The laminate lay-up according to claim 18, wherein thebottom second resin impregnated core sheet is subjected to the parchmenttreatment prior to being impregnated with resin.
 20. The laminate lay-upaccording to claim 19, wherein the bottom second resin impregnated coresheet includes a first side and second side, and the second side is alower surface that is ultimately exposed and bonded to a substrate, andwherein the second side is subjected to a parchment treatment.